During tablet manufacturing using fluid bed technology the present inventors discovered that the tablets produced were always free of bacteria even when the raw materials had bacterial counts in excess of 1000 CFU/g (CFU=colony forming units). In order to clarify which of the processing parameters was responsible for the apparent bactericidal effect, the inventors designed an experimental protocol which is described in general terms below.
The experiment was conducted in a Huttlin Turbojet Fluid Bed Coater (BWI Huttlin, Daimlerstrasse 7, D-79585, Steinen, Germany) with a 5 L processing container fitted with three bottom spray three-component spray nozzle jets and standard 20 micron filter bags. Samples of Lactobacilli were sourced from Chr. Hansen of 49 Barry Street, Bayswaster, Melbourne, Australia. Lactobacilli with Bifidus at a ratio of 1:1 was sourced from Gist-Brocade, Australia. These bacteria are anaerobes which easily perish in the presence of oxygen. The trial batch size of the fluidized bed was 4 kg, twice the weight recommended for the 5 L Huttlin Turbojet processing container used, to ensure the fluidized material was close to the processing containers filter giving the best chance for the bacteria to escape through the 20 micron filter. The solid core (tablet granule core materials) comprised 66% w/w dextrose, 13% w/w gelatin, 15% w/w starch. The spraying liquid containing bacteria comprised either 1.16×1012 CFU Lactobacilli, or 3.5×1012 CFU Lactobacilli/Bifidus, with 3% w/w mannitol, 1% w/w egg albumin, 1% w/w glycerol, 1% w/w sodium phosphate buffers and made up to 1000 ml with purified water.
The solid core material was loaded into the Huttlin Turbojet by vacuum and fluidized at a rate of 250 or 300 cubic meter of air/hour. Subsequently, the spray liquid was sprayed into the processing container at a rate of 30 gram/minute. The process was conducted at a product temperature of 40-45° C. The material was dried to less than 5% moisture content at a product temperature of 40° C.
It was discovered that running the experiment with a fluidisation rate set at 250 cubic meters of air/hour was not sufficient. At this rate the fluidized material crashed when 95% of the liquid was sprayed into the solid core. Fluidisation at a rate of 300 cubic meters of air/hour overcame this problem.
Samples of the granules obtained during this process were retained and the rest of the granules were compressed into tablets after blended with a standard tablet lubricant. The granules and the tablets were analysed to assess their live bacterial count. The results obtained are provided in Table 1 below.
TABLE 1Reportedactivity inTheoreticalReportedCFU/4 kgactivityactivity insample keptSamplein CFU/4 kgCFU/4 kgat 4° C. forDescriptiontime zerotime zero60 daysChr. Hansen1.16 × 10121.70 × 10111.64 × 1011GranulesChr. Hansen1.12 × 10124.40 × 1011  4 × 1010TabletGist-Brocade3.52 × 10129.80 × 10104.80 × 1010 (Lactobacilli only)Granules(No Bifidus detected)Gist-Brocade3.44 × 10126.00 × 10101.2 × 1010 (Lactobacilli only)Tablet(No Bifidus detected)
It was extremely surprising to detect the presence of viable bacterial cells in the samples after the treatment the bacterial cells were exposed to in the processing of the granules and tablets; heating, possible total ventilation through the 20 micron filter, mechanical milling, air drying and tablet compression. That a substantially high number of bacteria survived during these experiments did not elucidate why the tablets the inventors had previously produced were bacteria free. The results did, on the other hand, suggest a novel process to prepare samples or products containing live bacteria in a stabilized form.
The suppliers of the lactobacilli and bifidus cultures indicated that these bacteria are extremely temperature sensitive, and heat labile. When such cultures are processed using freeze-drying, bacterial counts are noted to drop by 90-99%. Further, the suppliers have indicated that the bacteria are also particularly sensitive to standard tablet compression processes and accordingly that a further drop in activity of the bacteria of approximately 99% may be observed.
Accordingly, the inventors have discovered a novel heat drying method which appears to be superior to known industrial methods of preparation, such as freeze-drying. The inventors have further found that bacteria processed in this novel manner (i.e. in micro-capsules) can survive tablet compression pressure around 5 to 8 tons/square inch.